From 43021c1aba12e3d8c0066b86a98d76f4c001f8dd Mon Sep 17 00:00:00 2001
From: mutouyun <orz@orzz.org>
Date: Sat, 1 Apr 2023 18:01:33 +0800
Subject: [PATCH] add: [imp] copy_cvref

---
 include/libimp/generic.h      | 38 +++++++++++++++++++++++++++++++++++
 test/imp/test_imp_utility.cpp | 18 +++++++++++++++++
 2 files changed, 56 insertions(+)

diff --git a/include/libimp/generic.h b/include/libimp/generic.h
index 0fc8dd6..54d1288 100644
--- a/include/libimp/generic.h
+++ b/include/libimp/generic.h
@@ -84,4 +84,42 @@ struct is_specialized : std::false_type {};
 template <template <typename...> class Tt, typename... A>
 struct is_specialized<Tt, Tt<A...>> : std::true_type {};
 
+/**
+ * \brief Copy the cv qualifier and reference of the source type to the target type.
+ */
+template <typename Src, typename Des>
+struct copy_cvref {
+  using type = Des;
+};
+
+template <typename Src, typename Des>
+struct copy_cvref<Src const, Des> {
+  using type = typename std::add_const<Des>::type;
+};
+
+template <typename Src, typename Des>
+struct copy_cvref<Src volatile, Des> {
+  using type = typename std::add_volatile<Des>::type;
+};
+
+template <typename Src, typename Des>
+struct copy_cvref<Src const volatile, Des> {
+  using type = typename std::add_cv<Des>::type;
+};
+
+template <typename Src, typename Des>
+struct copy_cvref<Src &, Des> {
+  using type = typename std::add_lvalue_reference<
+               typename copy_cvref<Src, Des>::type>::type;
+};
+
+template <typename Src, typename Des>
+struct copy_cvref<Src &&, Des> {
+  using type = typename std::add_rvalue_reference<
+               typename copy_cvref<Src, Des>::type>::type;
+};
+
+template <typename Src, typename Des>
+using copy_cvref_t = typename copy_cvref<Src, Des>::type;
+
 LIBIMP_NAMESPACE_END_
diff --git a/test/imp/test_imp_utility.cpp b/test/imp/test_imp_utility.cpp
index 9ab676b..93b0257 100644
--- a/test/imp/test_imp_utility.cpp
+++ b/test/imp/test_imp_utility.cpp
@@ -134,3 +134,21 @@ TEST(utility, in_place) {
   [](std::in_place_t) {}(imp::in_place);
 }
 #endif/*LIBIMP_CPP_17*/
+
+TEST(utility, copy_cvref) {
+  EXPECT_TRUE((std::is_same<imp::copy_cvref_t<int   , long>, long   >()));
+  EXPECT_TRUE((std::is_same<imp::copy_cvref_t<int & , long>, long & >()));
+  EXPECT_TRUE((std::is_same<imp::copy_cvref_t<int &&, long>, long &&>()));
+
+  EXPECT_TRUE((std::is_same<imp::copy_cvref_t<int const   , long>, long const   >()));
+  EXPECT_TRUE((std::is_same<imp::copy_cvref_t<int const & , long>, long const & >()));
+  EXPECT_TRUE((std::is_same<imp::copy_cvref_t<int const &&, long>, long const &&>()));
+
+  EXPECT_TRUE((std::is_same<imp::copy_cvref_t<int volatile   , long>, long volatile   >()));
+  EXPECT_TRUE((std::is_same<imp::copy_cvref_t<int volatile & , long>, long volatile & >()));
+  EXPECT_TRUE((std::is_same<imp::copy_cvref_t<int volatile &&, long>, long volatile &&>()));
+
+  EXPECT_TRUE((std::is_same<imp::copy_cvref_t<int const volatile   , long>, long const volatile   >()));
+  EXPECT_TRUE((std::is_same<imp::copy_cvref_t<int const volatile & , long>, long const volatile & >()));
+  EXPECT_TRUE((std::is_same<imp::copy_cvref_t<int const volatile &&, long>, long const volatile &&>()));
+}
\ No newline at end of file